a)[tex] 2^{x+1}*2 ^{3x-5}= 2^{4} \ \textless \ =\ \textgreater \ x+1+3x-5=4 =\ \textgreater \ x=2[/tex]
b)[tex] 3^{2x-1}* 3^{2x+1}=3^4 \ \textless \ =\ \textgreater \ 2x-1+2x+1=4 =\ \textgreater \ x=1 [/tex]
c)[tex] 5^{2x+1}* 5^{x+7}=5^2 \ \textless \ =\ \textgreater \ 2x+1+x+7=2 =\ \textgreater \ 3x=-6=\ \textgreater \ x=-2 [/tex]